Electrical apparatus



Feb. 5, 1929. 1,701,374

.1. M. KENDALL ELECTRICAL APPARATUS Filed June 1927 Inv ent or: Jam es M, Kendall by W His Attorney Patented Feb. 5, 1929.

UNITED STATES JAMES M. KENDAL 1 1,701,374 PATENT OFFICE,

ELECTRICAL APPARATUS.

- Application filed June 1,

My invention relates to electrical apparatus comprising a plurality of thermionic amplifiers or detectors, and has for its prin cipal object the provision or an improved ar-' rangenient for controlling the grid potentials of thermionic space discharge devices provided with cathode heating circuits connected in series and with anode circuits connected in parallel. I

When space discharge, devices are operated in parallel with their cathodes connected in 1 series to a source of heating current, difliculty is likely to be encountered due to the fact that a difference of potential exists between the various cathodes and the current is unequally divided between the parallel-connected anode circuits of the devices. In accordance with my invention, this difficult'y is avoided by the provision of an improved arrangement for maintaining between the grid and cathode potentials of the devices a relation which ensures that each device carries its proper share of the load current.

I My invention will be better understood from the following description When considered in connect1on=w1th the accompanying drawing, and its scope will be pointed out in the appended claims.

The drawingdiagrammatically illustrates certain details. of an amplifying and detecting apparatus wherein my invention has been embodied.

This apparatus comprises direct current leads 1 and 2, which are arranged to supply electrical power to the cathode heating circuits'of the space discharge devices 3 to 6, to the field winding 7 and operating winding 8 of a loud speaker 9, and to taps 10 to 12. It should be noted that the taps 10 to 12 may be connected to the anode circuits of a radio receiving apparatus through which electrical impulses are applied'to the input circuits of the devices 3 to 6.

Heating current is transmitted between the leads 1 and 2 through an adjustable-resistor 13, a control switch 14, and a pair ofparallel connected circuits which respectively comprise a resistor 15 connected in serieswith cathodes 16 and 17 of the devices 3 and 4 and a resistor 18 connected in series with cathodes19 and 20 of the devices 6 and 5. It

will of course be understood that, by reason of the series connections of the cathodes, the cathodes 16and 19 are maintained at a some- 1927. Serial No. 195,793.

whathigher potential than the cathodes i117 and 20. Due to this difference between the potential or the cathodes 17 and 20 and the current is diyided equally between the various devices only when the grids of the devic s areso biased that the grids of all the devices have substantially the same potential with respect to their respective cathodes.

Power is supplied to the operating winding 8 of the loud speaker9 from the leads 1 and 2 through the control switch 14, the anode circuits of the devices 3t-o 6, and a transformer 21. This power is controlled by electrical impulses applied to the grid or input circuits of the devices 3 to 6 through a trans former 22 which is provided with a secondary winding 23. It will be observed that the grids 24. and of the devices 4 and 5 respectively are connected tothe cathode circuit through a bias battery 26, resistor 27 for preventing parasitic oscillations in the grid cir cult and opposite halves of the secondary or sco'rm, NEW YORK, AssIeNoR To GENERAL ELECTRIC coM- 'I'ANY, A CORPORATION on NEW YORK.

- potential of the cathodes 16 and 19, the load of the bias battery 26 and impedance means 1 shown as resistors 30 and 31; that the grid '28 is connected to one end terminal-0f the secondary winding 23 through a capacity coupling shown as a condenser 32; and that the grid'29 is connected to the other terminal of the winding 23 through a coupling con-denser WVith these connections a bias potential dependent on the voltage of the battery 26 is maintained on the grids 24 and 25. The bias potential ofthe grid 28, however, is dependent on the adjustment of the connection between the battery. 26 and the resistor 30 and the bias potential of the grid 29 is likewise dependent on the adjustment of the connection between'the battery 26 and the resistor 31. It will-be understood without detailed explanation that by proper adjustment of the end taps of the resistors 30 and 31 any desired relation may be established between the grid bias potentials of the devices 3 to 6, and that the electrical impulses are applied to the grids 24 and 25 directly and to the grids 28 and 29 through the condensers'32 and 33 respectively. Under these conditions, the

proper division of the current between the devices 3 to 6 is readily maintained even though the cathode potential of the devices 3 and 6 differs from that of the devices 4 and 5.

What I claim as new and desire to secure by Letters Patent of the United States is 1. The combination of a plurality of parallel-connected space discharge devices provided with anode circuits and with cathode heating circuits connected in series, means arranged to bias the grids of said devices to different potentials, control current supply means connected between the grid and "athode of one of said devices through said. grid bias potential means, and a capacity coupling between said control current supply means and the grid of another of said devices.

2. The combination of a plurality of parallel-connected space discharge devices provided with anode circuit and with cathode heating circuits connect in series, means arranged to apply a predetermined bias potential to the grid of one of said devices and an adjustable bias potential to the grid of another of said devices, control current supply means connected between said bias potential and one of said grids, and a condensor connected between said grids.

3. The combination of a plurality of space discharge devices each provided with a cathode and a grid, a circuit arranged to connect said cathodes in series with one another, a source of bias potential connected to one terminal of said circuit and provided with end and intermediate terminals, control current supply means connected between said. cathodes and the grid of one of said devices through means comprising said end terminal,

an impedance means connected between said cathodes and the grid of another of said devices through said intermediate terminal, and a capacity coupling between said-grids.

4. The combination of a plurality of space discharge devices each provided with a cathode and a grid, a circuit arranged to connect said cathodes in series withone another, a source of bias potential connectec to one terminal of said circuit and provided with an end terminal and an adjustable intermediate terminal, control current supply means connected between said cathodes and the grid of one of said devices through means comprising said end terminal, an impedance means connected between said cathodes and the grid of another of said devices through said intermediate terminal, and a capacity coupling between said grids.

5. The combination of a plurality of space discharge devices each provided with a cathode and a grid, a circuit arranged to connect said cathodesin series with one another, a source of bias potential connected to one terminal 01 said circuit and provided with'end and intermediate terminals, a resistor, control current supply means connected between said cathodes and the grid of one of said devices through said end terminal and said resistor, an impedance means connected between said cathodes and the grid of another of said devices through said intermediate terminal, and a capacity coupling between said grids.

In witness whereof, I have hereunto set my hand this 31st day of May 1927.

JAMES M. KENDALL. 

